Social engagement, social support and social bonds can have positive health benefits, although the mechanisms for these effects are at present not well understood. We propose here to use the socially-monogamous prairie vole (Microtus ochrogaster) as an animal model to examine mechanisms for socially-induced changes in behavior and physiology. The proposed study postulates a novel mechanism through which even a brief social experience, possibly mediated in part by neuropeptide systems, can impact future behavior and brain function. Preliminary data reveal that exposure to an infant can significantly facilitate pair bonding, can release the brain hormone oxytocin (OT) and inhibit the activity of "stress" hormones from the hypothalamic-pituitary-adrenal axis. Here we propose to study regionally specific neuroendocrine changes that accompany pup exposure, focusing on neural systems, such as the amygdala, that are associated with social behavior and fear, and that are targets for OT, and a related neurohormone, arginine vasopressin (AVP). We also will further investigate the consequences of pup exposure through an analysis of subsequent social behaviors, including sociality to strangers and pair bond formation. Measures will include behavioral and neuroendocrine responses (measured by brain microdialysis, cFos and immunocytochemistry, and blood levels of OT, AVP and corticosterone). We will study both individual differences and gender-specific patterns of behavioral and neuroendocrine responding to pups to examine the hypothesis that these differences may reflect the actions of these hormones, including especially OT in females and AVP in males. Multiple measures focused around a simple paradigm (responses to a pup) allow an analysis of relationships among behavioral and neuroendocrine parameters, including behavior and physiology, which may share common neural substrates. Deficits in social behavior are a feature of several forms of mental illness, including autism, depression and schizophrenia, and may be associated with a vulnerability to substance abuse. The proposed study will contribute to our basic understanding of mammalian social behavior, and especially processes associated with parenting. In addition, these studies may help us understand neuroendocrine mechanisms underlying child neglect or abuse and why these may differ in males and females.